Numerical modeling of the initial stage of the generation of unsteady vortices from sharp corner in plane compressible flow

1994 ◽  
Vol 15 (8) ◽  
pp. 697-702
Author(s):  
Huang Dun ◽  
Yang Chun
Keyword(s):  
Numerical Modeling ◽  
Compressible Flow ◽  
Sharp Corner ◽  
Initial Stage

scholarly journals ПРИМЕНЕНИЕ МЕТОДОВ ЧИСЛЕННОГО МОДЕЛИРОВАНИЯ ПРИ ЭКCПЕРИМЕНТАЛЬНОЙ ОТРАБОТКЕ ЗАБОРНЫХ УСТРОЙСТВ ЦЕНТРАЛЬНОГО ТИПА

2019 ◽  
pp. 33-42
Author(s):  
Александр Николаевич Минай ◽  
Игорь Викторович Седых ◽  
Ирина Юрьевна Кузьмич
Keyword(s):  
Numerical Modeling ◽  
Large Scale ◽  
Engineering Practice ◽  
Launch Vehicles ◽  
Stage Of Development ◽  
Initial Stage ◽  
Scale Models ◽  
Hydrodynamic Processes ◽  
Definition Of ◽  
Semi Empirical

At the design of intakes of fuel tanks of launch vehicles in engineering practice, empirical and semi-empirical dependences are used for the determination of main parameters of the movement of liquid. However, the received from skilled data, empirical dependencies are applicable for a limited circle of tasks in which conditions (initial and boundary) are similar to for what these dependencies were received. Therefore, the calculated parameters of intakes it has to be validated by the results of experimental working off. Experimental working off intakes at hydrodynamic stands is, as a rule, carried out on natural tanks and their large-scale models (skilled designs) in terrestrial conditions. For confirmation of similarity of hydrodynamic processes, experimental working off the large-scale models is carried out on several skilled designs of different scales and several model liquids. Now, with the development of computer facilities and numerical methods of the solution of the differential equations of the movement of liquid, there was an opportunity to replace almost universal use of empirical dependences with more exact computing experiment. It, in some cases, allows reducing the quantity of the used skilled designs, terms of carrying out experimental working off, and, as a result, material expenses. The article presents results of the experimental definition of the static hydraulic rest of a component of fuel in skilled designs of a tank of the first step of carrier rockets with the central selection of a component and numerical modeling on mathematical 3D and 2D models of skilled designs (similar scale) are considered. The authors developed the calculated and experimental method of verification of results of numerical modeling allowing them to conduct necessary researches with the demanded accuracy. The offered approach allows improving the existing traditional method of experimental working off of intakes, already at the initial stage of development to optimize their parameters, to reduce the volume of necessary experimental working off and to lower time and material expenditure on its carrying out.

Reaction couples of ceramic thin films prepared by CVD

1988 ◽  
Vol 46 ◽  
pp. 798-799
Author(s):  
D.W. Susnitzky ◽  
S.R. Summerfelt ◽  
C.B. Carter
Keyword(s):  
Thin Film ◽  
Vapor Deposition ◽  
Chemical Vapor ◽  
Deposition Process ◽  
Solid State Reactions ◽  
Spatial Distributions ◽  
Diffusion Couples ◽  
Kinetics Studies ◽  
Ceramic Thin Films ◽  
Initial Stage

Solid-state reactions have traditionally been studied in the form of diffusion couples. This ‘bulk’ approach has been modified, for the specific case of the reaction between NiO and Al2O3, by growing NiAl2O4 (spinel) from electron-transparent Al2O3 TEM foils which had been exposed to NiO vapor at 1415°C. This latter ‘thin-film’ approach has been used to characterize the initial stage of spinel formation and to produce clean phase boundaries since further TEM preparation is not required after the reaction is completed. The present study demonstrates that chemical-vapor deposition (CVD) can be used to deposit NiO particles, with controlled size and spatial distributions, onto Al2O3 TEM specimens. Chemical reactions do not occur during the deposition process, since CVD is a relatively low-temperature technique, and thus the NiO-Al2O3 interface can be characterized. Moreover, a series of annealing treatments can be performed on the same sample which allows both Ni0-NiAl2O4 and NiAl2O4-Al2O3 interfaces to be characterized and which therefore makes this technique amenable to kinetics studies of thin-film reactions.

Decoration technique and surface physics

1978 ◽  
Vol 36 (1) ◽  
pp. 436-437 ◽  
Author(s):  
H. Bethge
Keyword(s):  
Diffusion Path ◽  
Special Importance ◽  
Surface Physics ◽  
Step Structure ◽  
Initial Stage ◽  
Special Cases ◽  
Atomic Surface ◽  
The Mean ◽  
Bulk Structure ◽  
Decoration Technique

Besides the atomic surface structure, diverging in special cases with respect to the bulk structure, the real structure of a surface Is determined by the step structure. Using the decoration technique /1/ it is possible to image step structures having step heights down to a single lattice plane distance electron-microscopically. For a number of problems the knowledge of the monatomic step structures is important, because numerous problems of surface physics are directly connected with processes taking place at these steps, e.g. crystal growth or evaporation, sorption and nucleatlon as initial stage of overgrowth of thin films.To demonstrate the decoration technique by means of evaporation of heavy metals Fig. 1 from our former investigations shows the monatomic step structure of an evaporated NaCI crystal. of special Importance Is the detection of the movement of steps during the growth or evaporation of a crystal. From the velocity of a step fundamental quantities for the molecular processes can be determined, e.g. the mean free diffusion path of molecules.

Nucleation and initial growth of Pd2Si crystals on Si(111)

1993 ◽  
Vol 51 ◽  
pp. 844-845
Author(s):  
Xianghong Tong ◽  
Oliver Pohland ◽  
J. Murray Gibson
Keyword(s):  
High Vacuum ◽  
Dark Field ◽  
Ultra High Vacuum ◽  
Initial Growth ◽  
Surface And Interface ◽  
Dark Field Imaging ◽  
Transmission Electron ◽  
Initial Stage ◽  
Effect Of Surface

The nucleation and initial stage of Pd2Si crystals on Si(111) surface is studied in situ using an Ultra-High Vacuum (UHV) Transmission Electron Microscope (TEM). A modified JEOL 200CX TEM is used for the study. The Si(111) sample is prepared by chemical thinning and is cleaned inside the UHV chamber with base pressure of 1x10−9 τ. A Pd film of 20 Å thick is deposited on to the Si(111) sample in situ using a built-in mini evaporator. This room temperature deposited Pd film is thermally annealed subsequently to form Pd2Si crystals. Surface sensitive dark field imaging is used for the study to reveal the effect of surface and interface steps.The initial growth of the Pd2Si has three stages: nucleation, growth of the nuclei and coalescence of the nuclei. Our experiments shows that the nucleation of the Pd2Si crystal occurs randomly and almost instantaneously on the terraces upon thermal annealing or electron irradiation.

Sign in / Sign up

Export Citation Format

Share Document